खालील विधाने पहा.
a. लाव्हारसात लोखंड व मॅग्नेशियम खनिजा पेक्षा सिलीका द्रव्याचे प्रमाण जास्त असेल तर त्याला अॅसिडक लाव्हा म्हणतात.
b. शिलारसात वाळूचे प्रमाण जास्त असल्यामुळे तो भूपृष्ठावर जास्त पसरत नाही.
c. पेगमॅटीटीक खडकात स्फटिक मोठे असतात.
d. बेसिक लाव्हा हा अतिशय घट्ट असतो.

The correct answer is Option C (a, b, c are correct but d is incorrect).

Key Points:
• Volcanology and Magma Types:
• Statement a (Correct): Acidic (Felsic) magma has high silica content (>65%) compared to iron and magnesium, giving it high viscosity.
• Statement b (Correct): Due to high silica/sand content, acidic lava is extremely viscous and sluggish, preventing it from spreading far over the surface and forming steep volcanic domes.
• Statement c (Correct): Pegmatitic intrusive igneous rocks cool very slowly underground from volatile-rich fluids, forming exceptionally large mineral crystals (often >2.5 cm).
• Statement d (Incorrect): Basic (Mafic) lava is rich in iron/magnesium and poor in silica, making it highly fluid and runny (low viscosity), NOT very thick.
• Thus, statements a, b, c are correct and d is incorrect (Option 3).
• Key Takeaway: Acidic magma is silica-rich and viscous (does not spread far); pegmatite has large crystals; basic lava is fluid (not thick).